OF THE TEETH. 143 



are entirely filled up, so that the tooth is one solid mass of two different 

 suhstances - 1 . 



Relation of Teeth to Food, 



The teeth of animals are not always answerable to the food they 

 eat. The horse and cow feed upon the same food ; a snail also lives 

 upon the same food, and the tooth of a snail is very different from the 

 teeth of either [cow or horse]. Nor do the teeth of animals correspond 

 with their stomachs. Animals that have nearly the same stomachs 

 have very different kinds of teeth. 



The formation of the mouth, so far as respects the teeth, seems to be 

 adapted to the catching or laying hold of the food. Thus, those animals 

 that live upon animal food have the shortest mouths, and their teeth 

 are regularly set ; but those that live on vegetables have their heads 

 long, much longer than is requisite for the number of teeth. Therefore 

 the jaws are prolonged to allow the catching teeth to be removed farther 

 from the grinders. 



Most land animals have the upper jaw the longer, overshooting the 

 under ; but this is not so much the case in fishes. In most of these 

 the lower jaw is the longer. The anterior parts of the mouth of a fish 

 is not [rarely] made for dividing 2 . 



Of Eating. 



Those animals that have no upper teeth I should imagine eat more 

 of the roots of grass than others, because they do not cut the grass, 

 but pull it, which brings it out by the roots in some measure. All ani- 

 mals that chew their food, have lips, which are to confine the food : but 

 those that swallow it without mastication have none. 



Motion of Lower Jaw. — In carnivorous animals there is not that 

 grinding motion of the lower jaw, in eating, that is to be found in 

 others : the articulation will not allow it, nor will the canine teeth ; but 

 still they have a little ; and the motion of the two condyles of the jaw, 

 in that case, is not forward, but from side to side, in a groove : this is 

 quite contrary in other sorts of animals ; for in them one condyle is 

 always the centre of motion, and the other condyle with the symphysis 

 of the jaw moves ; but in the former the symphysis is fixed and the 

 two condyles move. 



1 [A study of the Hunterian preparations, Nos. 333-349, 373-375, will much 

 assist in the comprehension of the above description, and will give the grounds of 

 the interpolated terms which seemed needful for the understanding of the text.] 



2 [The beaks of the parrot-fishes (Sear us) and globe-fishes (Diodon, Tetrodon) are 

 exceptions.] 



